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Cystic Fibrosis Trust

How is cystic fibrosis diagnosed?

Find out more about cystic fibrosis (CF) diagnosis, including the processes of newborn screening, carrier testing and antenatal testing.

Most cases of CF are therefore diagnosed at birth, but sometimes cystic fibrosis may not be diagnosed until later in life, especially in children and adults who were not screened at birth or who carry less common mutations which may not have been picked up through the screening programme. 

There are three main types of screening for cystic fibrosis: newborn screening, carrier testing and antenatal testing.

Newborn screening

This test involves a heel-prick sample of blood, taken as part of the normal Guthrie test carried out on all babies. The sooner cystic fibrosis is diagnosed, the sooner appropriate treatment can begin.

See the UK Newborn Screening Programme Centre for more information.

Carrier testing

A simple mouthwash or blood test can determine if you are a carrier of the defective gene that causes cystic fibrosis. This is important if your partner is a known carrier, or if a relative has cystic fibrosis or is a carrier.

Antenatal testing

Used early in pregnancy, this test is usually offered to mothers who are seen as being at a high risk of having a child with cystic fibrosis.

Other tests

There are a number of other ways of testing for cystic fibrosis, such as the sweat test (people with cystic fibrosis have more salt in their sweat) or a genetic test, where a swab is rubbed gently on the inside of the cheek to look for the faulty gene.

If your partner is a carrier and you would like to be tested, the genetic interest group has a list of useful services.

If a baby is born with the intestinal obstruction meconium ileus, this is a strong indicator of cystic fibrosis. Some 10 to 15% of infants with cystic fibrosis present symptoms within 24 hours of birth.


The Trust is committed to funding and supporting cutting-edge research to find new and better treatments for cystic fibrosis. Take a look at some of that work and the progress that is being made.

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What is cystic fibrosis?

Find out more about cystic fibrosis, its diagnosis and how it is treated, as well as useful links to our publications and other organisations who can help.

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